1. Field of the Invention
The present invention relates to machinery designs and supporting component integration (intercoolers, regenerator, combustor or heater and reheaters) for achieving a high thermal efficiency engine.
The engine is based on the Modified Ericsson cycle, capable of using low technology as well as advanced technology components, that are combined into various optional systems for power, efficiency, and ease of development considerations.
The above and other features of this invention will be more fully understood from the following detailed description of the engine, a discussion of various design options and the accompanying drawings.
2. Description of Related Art
The subject invention pertains to the selection of rotating and reciprocating machinery along with the integration of this machinery with intercoolers, a regenerator and a high temperature combustor or heater and reheaters to achieve a very high efficiency engine based on the Modified Ericsson cycle. This engine has the size and operating charateristics that are comparable to or better than current internal combustion automobile and truck engines. These include: (1) higher efficiency potential; (2) lower working fluid operating temperatures and pressures and thus lower exhaust gas pollutants; (3) external combustion that can use optional fuels such as natural gas, lower grade fuels other than high octane gas (kerosene, propane, butane) and gases derived from coal.
The Ericsson cycle, although not currently used for reasons to be discussed, remains an attractive cycle because it, like a Stirling, ideally achieves Carnot efficiencies when operated between given upper and lower temperature limits. Ericsson engines have been used in the past to a limited extent, however, the mean effective pressure was too low for it to compete with internal combustion or steam engines. In a non-flow cycle such as hot gas in a cylinder, the work is obtained through the action of a moving piston being acted upon by a variable pressure. The net average pressure, called mean effective pressure (m.e.p.), times the displacement volume of the cylinder represents the work produced in one stroke. Low m.e.p. results in a large engine for a given power and thus a heavier design.
A practical way to overcome the low m.e.p., in order to take advantage of this high efficiency cycle, is the incorporation of a supercharger using a high speed turbocompressor for the first stage of the cycle. This addition allows a compressor of much smaller size than a comparable reciprocating design to perform the gas compression and expansion at the low ambient pressures.
By combining a turbocompressor for the low pressures of the cycle and a multi-piston reciprocating engine for the high pressures of the cycle along with intercoolers, a regenerator, a combustor or heater and reheaters, various versions (stages) of the Modified Ericsson cycle can be achieved. The Modified Ericsson approximates the Ideal Ericsson isothermal compression by using multiple stages of compression, with intercooling between stages, and the isothermal expansion by using multi-power expansion (turbine) stages, with reheat between stages. The regenerator is used to recover the exhaust heat from the last turbine stage and deliver it to the final stage compressor discharge gas prior to entering the combustor or heater. A high efficiency (also called effectiveness) regenerator is a key component in a regenerative thermal cycle. However, as stages are added to a Modified Ericsson cycle, the regenerator effectiveness becomes less critical to the overall cycle efficiency. This significant factor makes a multi-stage Modified Ericsson engine very attractive for a regenerative cycle and the benefits will be discussed in more detail in the following section.